This invention relates to a nail puller of the type having relatively movable jaws for gripping a nail by its shank and a lever arm for exerting a pulling force on the nail.
Of the many types of nail pulling tools, the most well known is the claw hammer. Almost everyone has used a claw hammer to pull nails, and many are aware of the limitations of that tool for the function of pulling nails. Despite the many configurations of the claw, none successfully pulls nails with every attempt. This is so in part because the nail pulling structure (the claw) is integral with the nail driving structure (the head); this imposes geometric constraints on the design of the claw. Also, because the claw is designed to engage the head of the nail, it is of little or no use when a nail's head has been broken off or badly damaged, or if the head is small, as with a finishing nail. And because the head must be engaged, the claw sometimes reaches its limit of travel before the nail is extracted, in which case one has to use another tool, or place a shim under the hammer head, to finish pulling the nail. Other tools, such as pry bars having nail pulling features, suffer the same deficiencies, even though they may provide a longer stroke.
Another characteristic of claw-type nail pullers is that they pull the nail at an angle to the axis along which the nail was driven initially. This angularity increases the friction between the nail shank and the hole, causing an unnecessary increase in the required pulling force. 